1. Field of the Invention
The present invention relates to an apparatus for forming semiconductor devices, and more particularly, to a gas diffusion plate that allows process gases to be uniformly supplied into an ICP (Inductively Coupled Plasma) etcher.
2. Description of Related Art
The semiconductor devices, such as a LSI (Large Scale Integrated), a memory IC (Integrated Circuit) and other logic elements, are generally fabricated by repeated depositing and etching processes. In the most recent, a high density plasma (HDP) is applied for etching the semiconductor device in an etching apparatus, for example, an inductively coupled plasma (ICP) etcher. In the etching apparatus, e.g., the ICP etcher, a method of applying process gases is classified as two types; an edge injection type and a shower head type.
FIG. 1 schematically illustrates a diagram of an edge injection type ICP etcher according to a related art.
In the edge injection type ICP etcher shown in FIG. 1, an ICP antenna 120 is disposed over a chamber cover 112 made of ceramic. Although the chamber cover 112 has a plate shape in FIG. 1, the chamber cover 112 can have a dome shape. A chuck supporter 160 connected to an RF (radio frequency) power supply 150 is disposed at the bottom of a chamber 100. The chuck supporter 160 acts as a cathode in the ICP etcher. An electrostatic chuck (ESC) 140 is disposed on the chuck supporter 160, and thus a semiconductor wafer (not shown) is fixed into the electrostatic chuck 140 by static electricity during the process. Meanwhile, process gases are supplied into the chamber 100 from edge injectors 130 that are on a chamber wall 110. The edge injectors 130 are connected to gas-supplying passages (not shown) that are installed in the chamber wall 110 so that the process gases are injected from the edge injectors 130 throughout the gas-supplying passages (not shown).
In the edge injection type ICP etcher described above, there is enough room between the chamber cover 112 and the electrostatic chuck 140, and the room therebetween is wide enough to obtain the uniformity of etching process under the pressure of less than 10 mT. However, in the recent etching process, particularly during the process of etching the oxide film, the room between the chamber cover 112 and the electrostatic chuck 140 becomes narrower in order to control the dissociation mechanism of the etching gases.
If the edge injection type ICP etcher shown in FIG. 1 has the narrower space between the chamber cover 112 and the electrostatic chuck 140, the supplied process gases hardly reach a central portion of the semiconductor wafer during the process and most of the supplied process gases are ejected through a gas outlet (not shown) that is connected to a pumping device (not shown). To overcome these disadvantages, the shower head type ICP etcher is generally and widely used.
FIG. 2 schematically illustrates a diagram of a shower head type ICP etcher according to a related art. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts.
In the shower head type ICP etcher shown in FIG. 2, an ICP antenna 120 is disposed over a chamber cover 112 made of ceramic. Although FIG. 2 shows the chamber cover 112 having a plate shape, the chamber cover 112 can also have a dome shape. A chuck supporter 160 connected to an RF (radio frequency) power supply 150 is disposed at the bottom of a chamber 100. The chuck supporter 160 acts as a cathode in the ICP etcher. An electrostatic chuck (ESC) 140 is disposed on the chuck supporter 160, and then a semiconductor wafer (not shown) is fixed into the electrostatic chuck 140 by static electricity during the process. A shower head 132 is installed in the chamber cover 112.
Unlike the edge injection type ICP etcher shown in FIG. 1, the shower head type ICP etcher of FIG. 2 supplies the process gases into the chamber 100 through the shower head 132. The shower head 132 is located right above the central portion of the semiconductor wafer (not show) and has a plurality of gas injection holes (not shown) therein so that the process gases are injected from the shower head 132 throughout the gas injection holes (not shown).
Meanwhile, in these days, the semiconductor wafer tends to become larger to have a diameter of about 300 mm, and the room between the chamber cover 100 and the electrostatic chuck 140 also tends to be narrower. Therefore, although the above-described shower head type ICP etcher is used to let the process gases to reach the central portion of the semiconductor wafer, the uniformity of etching process is hardly obtained because the gas injection holes of the shower head 132 provides the different pressure of the injecting gas depending on where the gas injection holes are disposed. Namely, the amount of gas and the gas injection speed are different among the gas injection holes of the shower head 132.